h. 
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so be ad- 
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ter screw. 
place by a 
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marks is 
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| provision 
| the map 
entially a 
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1ed to any 
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vas devel- 
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| principal 
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e depth of 
  
     
   
  
PHOTOGRAMMETRIC ENGINEERING 17 
(96-1& 
F1G. 4. Wide-Angle Multiplex Equipment. 
field is from 270 to 450 mm. projection 
distance. Thus, the optimum plotting 
scale is approximately 2.4 times the photo 
scale for 6 inch focal length photography 
and approximately 1.8 times the photo 
. scale for 8$ inch focal length photography. 
Dichromatic projection and observation is 
utilized to give the operator a three-dimen- 
sional view of the terrain. The illuminant 
is a 20 volt, 100 watt incandescent lamp 
with condensing lens system. 
The reduction printers are nominally 
  
Fic. 5. Wide-Angle Reduction Printer. 
distortion free and have fixed reduction 
ratios of 0.308 +0.2 per cent for 6 inch 
focal length photography and 0.219 40.3 
per cent for 8$ inch photography. 
The supporting frame is designed to sup- 
port 9 projectors when mounted on the 
cast aluminum plotting table, providing 
means for bridging control. 
Prior to the development of the Wide- 
Angle Multiplex equipment, this was the 
standard photogrammetric instrument of 
the U. S. Army for compiling topographic 
maps. 
Wide-Angle Multiplex 
The wide-angle Multiplex equipment 
(Figure 4) is designed for use in compiling 
topographic maps from 9 by 9 inch photo- 
graphs exposed with a 6 inch focal length 
metrogon lens. The standard equipment 
consists of vertical projectors, a variable 
ratio reduction printed, single and double 
supporting frames, cast aluminum plotting 
table, tracing table and accessories. The 
projectors have a principal distance of 
28.182 mm. and accommodate 54 by 54 
mm. diapositives. The projection distance 
to the plane of best definition is 360 mm. 
Usable depth of field is from 270 mm. to 
450 mm. projection distance. Thus the 
optimum plotting scale is approximately 
2.4 times the scale of 6 inch focal length 
photography. A 100 watt, 20 volt incan- 
descent lamp and condenser provide the 
illumination in the projector. Dichro- 
matic projection and observation is utilized